The invention relates to a master suitable for the manufacture of electroplated negative copies of metal.
The negative metal copies are hereinafter referred to as father matrices. The father matrices are usually manufactured from nickel or copper and in turn are used for making further copies. For example, the negative father matrices are used to manufacture positive metal copies known as mother matrices. Negative son matrices are manufactured from the positive mother matrices and are used to manufacture copies of the master which are wholly synthetic resin or which have a synthetic resin coating. Such copies are, for example, information carriers such as phonograph records, or in particular optical components such as mirrors, lenses, prisms and the like.
The optical components preferably comprise a supporting member of, for example, glass or quartz. A coating layer of, for example, a light-cured synthetic resin is provided on one side of the supporting member. The surface of the coating layer is the negative of that of the son matrix. The negative father matrix may also be used for making positive copies of a synthetic resin.
According to a current process of manufacturing a master for an optical component, the surface of an aluminum alloy disc is machined to the desired shape, for example an aspherical shape. It is not possible, however, to make the surface of an aluminum alloy super smooth by precision machining. The surface has irregularities in the form of micropits. The surface is not of optical quality.
Another serious disadvantage is that only one father matrix can be manufactured from the master. For this purpose a metal peel, for example a Ni peel or a Cu-peel, is grown on the treated surface of the master by electroplating. The aluminum alloy is then dissolved, and hence the master is lost.
A master for phonograph records is manufactured according to a known method by providing a lacquer layer on one side of a supporting plate, for example a metal or glass plate. An information track is cut in the lacquer layer with a chisel.
The master is provided, on the side of the lacquer layer, with an electrolessly deposited metal layer, for example a Ag layer. A Ag layer can be provided by a chemical metallization process (plating process) by treating the surface, simultaneously or successively, with an aqueous silver salt solution and an aqueous solution of a reducing agent.
A thicker metal layer, for example a Ni layer or a Cu layer, is provided by electroplating on the electrolessly deposited metal layer. With the master plate is finally removed, the lacquer layer is destroyed. Therefore, in this method the master can be used only once.